Color photography



May 30, 1950 E J, coo- 2,509,232

COLOR PHOTOGRAPHY Filed NOV. 26, 1946 EMULSION FILM COATED WITH INCORPORATING EMULSION FORMER PRINTING LIGHT l l EMULSION INCORPORATING MAGENTA COLOR E I-EEERESN COAT FORMER AND NEGATIVE SECOND FUGITIVE YELLOW EMULSION DYESTUFF PRINTING LIGHT l l l EMULSION GREEN REcoRD INCUOERIZ%RALHNG EEEZI TIJE COAT EERMER kIID THIRD FUGITIVE YELLOW EMULSION DYESTUFF PRINTI e LIG I TI

RED RECORD DEVELOP ALL COLOR AND SEPARATION NEGATIVE THREE A S SILVER IMAGES WITH COLOR DEVELOPER }FIN|SHED IMAGES fltlorney;

Patented May 30, 1950 UNITED STATES PATENT OFFICE COLOR PHOTOGRAPHY Application November 26, 1946, Serial No. 712,245 In Great Britain November 28, 1945 12 Claims.

This invention relates to the production of coloured photographic images and more particularly to the production of motion pictures in colour.

In the production of coloured photographic images both two-colour and three-colour reproduction have been extensively utilized as well as, to some extent, the addition of a fourth image for special purposes. There are two principal methods which have been used for the production of coloured photographic images.

In one of these methods a multi-layer sensitive material, usually consisting of three distinct emulsion layers with interposed filter layers, is printed by a single exposure from a multicoloured image. This method requires the provision of multi-layer material having colour sensitive emulsions and dyed filter layers and requires extreme consistency in the coating of the very thin layers of which it is composed. If the processing of the material is to be in any way comparable with ordinary black and white material appropriate colour-forming materials must also be incorporated in the colour sensitive emulsions; the introduction of these is in addition to that of the necessary sensitizers. Such additions add greatl to the complexity and cost of manufacture of the colour film.

An alternative to the addition of appropriate colour-forming materials is available. This however involves the use of a rather complex processing technique the purpose of which is to convert the component silver images, usually by reversal of the original exposure, into the required coloured images. Such processing involves selective treatment of the superposed emulsion layers with separate colour developing baths. Controlled penetration can be utilized by appropriately loading the colour developing baths. There are also available certain colour sensitizers which retain their distinctive colour sensitivity after development of the multi-layer material; this makes it possible to selectively expose the silver halide layers with the aid of filtered light, and thus in turn to print and tone the layers of the multi-layer material.

The second general method depends upon the successive production of the colour images by means of the transfer of dye images or the successive production of developed silver images which are in turn toned to the appropriate colour images. This general method involves a considerable departure from the technique of black and white work and requires a set of colour separation negatives with which to work. Nevertheless it has many features and advantages which render it of considerable value.

In one form of operating this second general method for the production of cinematographic film ordinary positive film is used solely for the provision of the sound track and, if desired, to provide a grey print from one of the colour separation negatives to emphasize the definition and gradation of the final composite image which is obtained by the transfer of yellow, magenta and blue-green impressions from a set of dyed relief films which are previously prepared, one for each colour image to be impressed, from the corresponding colour separation negatives. Not only have the dyed relief films to be first prepared but the dye transfer processes are diflicult to operate since each involves the maintenance to accurate registration for a period of about 1 minute during which the relief film and the receiving film must be held in intimate contact and while they are travelling together at a speed which may be of the order of feet per minute.

A second form of the second general method is described in British Patent 585,477 in which there is disclosed a method of producing a threecolour image which is especially suitable for cinetamographic work when three-colour separation negatives are available. According to the process of this application a multi-coloured photographic image is produced by printing a silver halide emulsion layer from a first colour separation record, developing and colouring to produce the required positive colour record, coating the layer containing the first formed colour record with a composition containing silver halide and the same emulsion colloid as that of the emulsion layer so as to produce, on drying, a second silver halide emulsion layer directly superposed upon the image-containing layer and having a substantially normal weight of silver halide and a colloid/silver ratio (based on the silver nitrate used in its production) of not more than 1.5 to 1, printing from a second colour separation record, developing and colouring to produce the required positive colour record, the sequence of formation of the colour images being chosen with respect to the chemical and image-wise desensitizing properties thereof that the relative density and the normal individual colour characteristics of the first-produced image are maintained substantially unimpaired during the subsequent processing. When this process is used for the production of three colour images, after producing the second image as outlined above a further coatin of emulsion is applied in substantially the same way, printed and coloured to produce the remaining positive colour record to complete the three-colour image, the same properties determining the sequence in which the formation of the colour records is carried out. By using emulsions having a colloid silver ratio of not more than 1.5 to 1 satisfactory adhesion between the emulsions is obtained, reticulation and frilling being avoided and, in addition, wash-.

ing of the film can be achieved in a minimum of time.

This process has been found'to possess-several important advantages. Three .colour .motion pictures can be made utilizing ordinar positive stock as starting material with only two coating steps, both of which are relativelyieasytoper form. With reasonable attention to processing details extremely good reproduction can be consistently obtained. Ilhe process does however involves threeiseparate printing and three separate processing .stagesandzthe latter, while not objectionable, tend to :make the processing cost high.

The present invention seeks to provide amodi- .fication ofthis prior process lin whi'ch certainoi :the, processin stages are eliminated.

According to the present? invention, a process for the'production :of a, .mu'lti-coloured :photographic imageicomprises. coatinga" photographic Tbase material lWith;a,ifiISt composition containing axsilver halide and acsubstantially :nommobile 1 colour former. dispersed in .aiphotograp'hic' :emulsion colloid, printing fromafirstscolorseparation'record, coating the :printed emulsion with:

a second compositionicontaining a silver :halide and a, second substantially cnoni-mobile .colour "Lformer disp'ersed'in the same photographic:emul- .sion'colloid as that'ofsaid firstlcompositioniso"as to produce, on'drying, a second silver halide emulcolour separation'negative of: a three-colour set,

' coating said emulsionj'layer with ase'cond-composition=ccntaining silver halide andasecond v substantially non-mobile colouriformer dispersed in-the same photograph emulsion colloid as that offsaid'first applied composition so as to produce,

on drying, a'secondemulsionlayer, superposed upon'said first emulsion, and containing a substantially normal coating weight of: silver halide, printing from the second colour separation nega- "tive of said three-colour set, coating said second emulsionlayer with a third composition containing silver halide and a'third'substantially nonmobile colour former dispersed in the same photographic emulsion colloid as that of the'first and second'applied compositions so as to produce, on drying, athird emulsion'layer superposed upon 'said second emulsionllayeriandcontaining a substantially normal coating weight of silver halide, the first,'second and third colour formers being so a chosen that upon development and coupling imageshave been produced andithe whole set developed simultaneously and then coupled with =-the same colour developerto give a set of colour record images each of which-is of the correct hue.

Thecolour developmentstage may be carried developer 'to;givethe desired colour images. ca-result. it is-not necessary to develop-each latent image as. it isprinted. Instead the additional with the said coupler subtractive images of correct hue are obtained, printing from the third colour separation negative of said three-colour set, simultaneously developing the three successively produced latent images and coupling with a coupler to simultaneously produce the three icolour images.

According to afeature of the invention the applied emulsion layers may have a colloid/silver .ratio (based on the silver nitrate used in their ,production) of not more than 1.5:1 and, preferably, 'of approximately 1:1.

The. present invention is similar to that described'in BritishPatent 585,477 in that it proceeds by thebuilding up of 9, multi-layer material each layer of which contains one of the component images. of'th'e'multi-colour image but differs therefrom in that the colour formers which are present in the emulsion layers are so chosen that they can all be developed with the same colour .As

layers built up, each containing the appropriate latent image 'until the complete set of latent out directlybut on account of the fact that the .kind of colour developers :contemplated'have, in

general, alow developing potential it is preferred first todevelop the three latent images in an ordinary black-and white developer such as one-based upon metol and-hydroquinone or-amidol, to convert .the 'resulting imagesiinto silver halideyfor examplaby treatment with a solution .of potassiumzferricyanide and'potassium bromide, to reexpose andthen redevelop-with the colour developer after-which the: silver. images -may beremoved by Farmerstreduccr;

Initial development witlran ordinary blackand amount of reduced silver canbe moreeasily controlled and. greatericonsistency'is possible than when developing agents of the-paraphenylene diamine type .are 'usediin:.'the 'first .instanceas these are extremelysusceptible to the bromide concentration, a. factor whichis extremely difficult tocontrolzin' processing work. 'On: the other hand redevelopment, the aextentv of which is determined bythe'amountof silverihalide present in*the image, can be "fully controlled and .iside- "black and white image.

pendent only upon the density of the original The colourfonners usedaccording to the present invention should be substantially non-mobile.

. Several methods have been "developed in recent years for rendering colour formerssubstantially non-mobile, the principalones being the introduction into the molecule of the colour former of one "or more groupswhich impart substantive properties with respectzto thephotographic emulsion colloid employed and the chemical and/or physical association of the colour former with some other relatively large molecule which in- "creases'the efiective size of the molecules and so substantially reduces their mobility. Thus there may be usedcolour formers containing alkyl sub- :stituents having at least five and preferably from twelve to eighteen carbon atoms or the colour 'former may have been combined by chemical reaction with a suitable residue such as that of a high molecular weight water-permeable but water-insoluble natural or synthetic resin, that of a sterol, that of a substance of the cyclic methane series, that of a, polypeptide, that of a, highly polymeric carboxylic acid, that of a polymeric material of which a carboxylic acid is a component or that of a carbohydrate.

The colour formers are so chosen that upon coupling with the selected colour developer colour images of the correct tone are obtained. Since all the images are developed simultaneously it follows that, in general, any desired order of printing the images may be adopted since such considerations as desensitization and degradation of an already formed colour image do not arise in the present process.

The process can be conveniently carried out using gelatine emulsions of normal characteristics having incorporated therein the said colour formers but preferably the emulsions employed are the emulsions of reduced gelatin silver ratio described in British Patent 585,477. The use of these emulsions not only enables the three distinct images to be accommodated within a minimum of depth but avoids any tendency for reticulation and frilling to occur due to swelling during processing as described in that application and also to be carried out in a minimum of time due to the reduced overall thickness of the multi-layer emulsion being treated.

The process of the present invention utilizes as starting material a film base material (e. g. pyroxylin or cellulose acetate strip material) to which is first applied a conventional primer. After removing the volatile solvent of the primer composition, a silver halide photographic emulsion composition, preferably having a gelatine/silver ratio of about 1:1 and containing a suitable concentration of a substantially nonmobile yellow colour former is applied. Examples of suitable yellow colour formers are terephthalolyl bis-acetanilide, benzoyl acetanilide, 5 (4 stearyl amidobenzoylacetamido) isophthalic acid and 4-methoxybenzoy1acetd l-(2- methylstearylamino 4' carboxyphenol) amide. The layer is preferably coated at such a thickness as to produce, on drying, a substantially normal coating weight of silver halide. By substantially normal coating weights of silver halide are meant those containing from 40 to 80 milligrams, and preferably 50 to 60 milligrams, of silver per square decimeter of coating. After drying this layer is printed from the blue record separation negative. The printed material is then coated with a second silver halide emulsion composition, preferably having the same or substantially the same silver/gelatine ratio as that first applied and containing a substantially non-mobile magenta colour former. Examples of suitable magenta colour formers are 1-(4-stearylamino-phenyl)- S-methyl-B-pyrazolone, l-(4'-phenoxy 3 sulphophenyl) -3-heptadecyl 5 pyrazolone, 1- (3- sulphophenyl 3 (4" stearyl-amido-phenyl) 5- pyrazolone and 4(1S-stearyl-fi-carboxypropionamido)-benzoylacetonitrile. This layer is also preferably coated at such a thickness as to produce an emulsion layer containing a substantially normal coating weight of silver halide. After setting and drying this layer is printed, in register, from the green record separation negative. The multi-layer material, now containing two latent images is coated a third time. The third coating is with a silver halide emulsion composition having emulsion characteristics similar to those of the first and second applied compositions but containing a substantially non-mobile bluegreen colour former. Examples of suitable bluegreen colour formers are di-(2.8-dihydroxy-3- naphthoic acid) benzidide, naphthalene-l-hydroxy-z-stearyl carbonamido 4 sulphonic acid, naphthalene-l-hydroxy 2 N (dodecylcarbonamido) -4 sulphonic acid, naphthalene 1 hydroxy 2(2m'ethyl stearylamino 5 sulphophenyl) carbonamido and naphthalene l-hydroxy 2 carbon (N stearyl N -i.sophthaly1) amide. This layer is also preferably coated at such a thickness as to produce an emulsion containing a substantially normal coating weight of silver halide. The multi-layer material, after setting and drying, is printed, in register, from the red colour separation negative and is ready for development.

Development, as already indicated may be by either of two methods. In the first method development of all three images may be carried out with a bath containing para-diethyIl-aminoaniline as colour developer. This colour developer is used in the present case since with all the above named colour components it gives dye images of the correct hue. Other paradialkyl aminoanilines may be used. The development bath is preferably kept in a state of thorough agitation but free from aeration throughout the development.

In the second and preferred method of development the silver images are simultaneously developed with a conventional metol-hydroquinone developer. This is controlled so as to prevent development being carried too far in view of the intention to subsequently redevelop. The developed material is then treated with a bath containing potassium ferricyanide and potassium bromide to reconvert the developed material to silver bromide. The image is then re-eXp-osed and developed again in the colour developer. By proceeding in this way much better control of the formation of the colour images and greater consistency has been found to be possible.

In printing the second and third images it is desirable to take steps to avoid any further action by the printing light in the stratum or strata of the already formed latent image or images. To this end a fugitive dyestufi' such as tartrazine may be incorporated in the second and any subsequently applied emulsion compositions. An alternative is to print the emulsion layers using ultra-violet light or to print the emulsion layers containing a fugitive dyestufi using ultra-violet light. Fugitive dyestuifs such as tartrazine are readily eliminated durin the subsequent processing especially when the applied layers are of reduced colloid/silver ratio.

In practising the process of the invention a silver halide emulsion may be prepared as follows. A solution containing the following is prepared and brought to 70 (3.:

Potassium bromide gms Potassium iodide gms 5 Gelatine -gms- 50 Water (distilled) ccs 1700 To this solution there is gradually added a solution of 200 gm's. of silver nitrate in 2 litres of distilled water. This solution is also at about 70 C. and the addition of the second solution to the first will occupy about 10 minutes. The mixture is stirred and maintained at 70 C. for a further 20 minutes to permit of ripening. At the end of the ripening period the emulsion is cooled as rapidly as possible to 45 C. at which temperature 50 gins. of washed gelatine is added and stirred into' the emulsion. Whenthoroughtdispersion of, the added gelatine has;.been.achieved anhydrous sodium'sulphate is added .to the emulsion until the silver halides. and the gelatine have been. precipitated." When the precipitate has settled it. is collected, broken up and'washed in water until substantially all the soluble potassium bromide has 'been'removed. The washed material is then redispersed. at about 60 C; in suflicient. water containing 100 gms. ofgelatine to bringJthe total weight of the emulsion to 3. kgm.- After redispersion the emulsion is allowedto after-ripen, the'optimum-time being determined by prelimi'-. nary testinge At the-conclusion= of the afterripening the. emulsion'is .cooled rapidly to 40 C. and stored until required for use.-

Prior' to coating the following additional ingredients:aremixed-into each-litre of the emuls-ion:

1 cc oi a-% solution of saponin in methyl alcohol 10 cos. of a 5% aqueous solution of chrome alum 30-50'ocs. of a 5% aqueous solution of the selected colour former obtainedby dissolving the colour component in aqueous caustic soda The choice of the colour iormerwilldepend upon the positive colour record which is to be-obtained. To secure uniform dispersion. or the colour former it is pr'eferredto use a high'speed mixer. The pH of. the emulsionis brought .back to that prior to the additions with hydrochloric acid.

. The starting material is a-base material, shown at A on the flow sheet such as a nitrocellulose or cellulose acetate. This is first coated with a primer andthen-with a silverhalide-emulsion containing the selected colour former. Prefer-, ably the emulsion employed is one having agelatine/silver ratio of not more than 1.5 to 1 and advantageously about 1 to l. The emulsion is coated in-such an amount as to produceon drying an emulsionrlayer containing a substantially normal coating, weight of silver. halide i. e. from 40-80 milligrams ofsilver per square decimeter, preferably 50-60=milligrams per square decimeter. Afterv drying the emulsion is printed'from-the appropriate colour. separation. negative. Thus if the selected colourformer incorporated into the emulsion is a yellow colour former (as shown at B on-the flow sheet) the colour separation nega-- tive from which it-is printed is the blue record separation negative (as at C 0n the flowsheet). After printing, and without developing, the printedemulsion is coated with a second emulsion which preferably has been prepared in a similar manner to the first emulsionbut contains a colour former from which an appropriately coloured image can be obtained when coupled 'with the same coupler as the first colour. The second emulsion may have the same gelatine/silver ratio as the first emulsion or it may differ therefrom.- In order to avoid reticulation and frilling in the developing stages it is preferred to use an emulsion having a gelatine/silver ratio of not more than 1.5 to 1 and preferably about 1 to 1. The second, emulsion may have incorporated therein aiugitive dyestulT; such as tartrazine, which restricts the action of the printing light to the emulsion. Alternatively the second image may lie-printed using ultra-violet light. The second emulsion may contain the'magentacolour 'former (D on the flow sheet) and, in that case; it is printed from the green record separation negative, as shown at E on theflow sheet.

. After the second printing: and again without developing; the second printed emulsion-is coated with a-third emulsion whichpreferably has been. prepared in the same:manner-as thei first. and second emulsions but contains a colour'former for the remaining colour-image which has yetto be obtained and which will. yield the-correct hue when coupled with the-same coupler as the first and second colour former. Preferably theemulsion has thesame gelatine/silverratioasthe second emulsion; This: emulsion alsolmay haveincorporated therein a fugitive dyestuff; such as tartrazine; which restricts theactionof the-print-' ing. light to the r-emulsionz' Alternately, it alsomay be printed using ultra-violetdight. The third emulsion may contain the :blue colour.for-= mer (Fonthe'fiowsheet), in which case it. is printed from the red record separation negative: (asshown at G on the-flow sheet).

It willbe understood that the order of printing thesimagesneed not necessarily be that outlined. Thecessential point is to obtain three emulsion layers each of which contains anappropriate colour former and has beenprinted froma colour separation record which is complementary to the positive colour record'which will be obtained ondeveloping- (or redeveloping) withthe coupler. The colour formers. employedmust be-non-mobile. or; substantially so and-it isspreferred'to use those containing at least one long aliphatic chain,'such as a stearyl group, and-at least. one solubilising group, such as a sulphonic orcarboxylic group in the molecule. Examples of such-colour components have been-given above.

The three layer film containing the threelatent images is now ready for development and this may proceed asfollows. A-bath is made up contain- Para-diethylaminoaniline sulphate gms 3 Sodium sulphite gms 2 Potassium carbonate -1 gms 75 7 Potassium bromide gms 2.5 Water to make; litre 1 Potassium ferricyanide gms l0 Ammonia 28% ccs 10 Water to make litre 1 after whichthefilmis again rinsed (I on the flow sheet) and'then treated with'a strong aqueous solution (about. 20%) of-"sodium thiosulphate (-G-f on; theflovr sheet). 7

As previously-indicated, however, it is preferred first to develop all three images to: silver in a metol -hydroquinone developer. This is made as follows:

Me'tol gms .1.5 'Sodium sulphite s gms '75 Hydroquinone gms 2.5 Potassium; bromide .gm 0.5 Water to make litre 1 The above solutionis adjusted to a pH of 10.2'by addition of sodium or potassium carbonate. The filmcarrying the threelatent images is developed in this solution, washed and fixed. The three metallic silver images are then converted to silver bromide by treatment with the following bath:

Potassium ferricyanide gins..- 20 Potassium bromide gms Water to make litre 1 when fully bleached, the film is rinsed and exposed to white light and then the colour images are developed in the para-diethylaminoaniline bath given above, after which the images are bleached and silver removed with sodium thicsulphate as outlined above.

More than one colour component may be incorporated into any one of the applied emulsions so long as upon colour development an image of the correct hue is obtained. Thus a mixture of 5-(4'-stearylamidobenzoylacetamido) isophthalic acid and e-methoxybenzoylacet-N-(2'-methylstearylamino-'-carboxyphenyl) amide may be used together as the colour components for the yellow image when the developer is a paradialkylaminoaniline such as paradiethylaminoaniline.

The process is applicable also to the formation of colour positives from the negatives of a two-colour process. Such process may be operated in the same general way as that described using the appropriate colour components. A suitable colour component from which to produce a yellowish-red positive colour record, when using diethylaminoaniline as the colour developer, is 1 (5-sulpho-3' -stearylaminophenyl) -3-methyl-5-pyrazolone. The blue-green colour components previously exemplified may be used in the emulsion for the second image.

At any stage after the final coating of the film a protective outer supercoating of emulsion or of a lacquer may be applied to the film to preserve it from damage by abrasion. A gelatine emulsion may be employed or a transparent lacquer having a basis of a film-forming material which will adhere to gelatine, such as a polyvinyl alcohol lacquer.

The invention can also be used for the production of images in which two or four images are produced on a single side of a base material and also when three or more images are produced by coating both sides of the base material. The general procedure is exactly as outlined, a suitable choice of colour components for coupling with a single coupler being made depending upon the colours desired in the positive records to be produced.

What I claim is:

l. A process for the production of a multicoloured photographic image which comprises coating a photographic base material with a first composition containing a silver halide and a colour former which is substantially non-diffusing under the process conditions dispersed in a photographic emulsion colloid, printing from a first colour separation record, coating the printed emulsion with a second composition containing a silver halide and a colour former of said nondifiusing type but adapted to produce a different coloured image, dispersed in the same photographic emulsion colloid as that of said first composition so as to produce, on drying, a second silver halide emulsion layer directly superposed on said printed emulsion, printin in register from a second colour separation record, simultaneously developing the successsively produced latent images with a developer capable of forming dyes from said colour formers and removing developed silver from the images.

2. A process according to claim 1 in which the concentration of the ingredients of the second applied composition is such as to produce a silver halide emulsion layer having a colloid/silver ratio based on the silver nitrate used in its production of not more than 1.5:1.

3. The process according to claim 1 in which the photographic emulsion colloid is gelatine.

4. The process according to claim 1 in which the colour formers employed each contain at least one aliphatic group containing at least five carbon atoms and at least one water-solubilizing group in the molecule.

5. A process for the production of a multicoloured photographic image' which comprises coating a photographic base material with a first composition containing a silver halide and a colour rormer which is substantially non-difiusing under the process conditions dispersed in a photographic emulsion colloid, printing from a first colour separation record, coating the printed emulsion with a second composition containing a silver halide and a colour former of said nondiffusing type but adapted to produce a different coloured image, dispersed in the same photographic emulsion colloid as that of said first composition so as to produce, on drying, a second silver halide emulsion layer directly superposed on said printed emulsion, printing in register from a second colour separation record, simultaneously developing the successively produced latent images with a developer incapable of forming dyes from said colour formers, removing unused silver halide, reconverting the developed silver images into silver halide, reexposing and developing with a developer capable of forming dyes from said colour formers and removing developed silver from the images.

6. A process according to claim 5 in which the concentration of the ingredients of the second applied composition is such as to produce a silver halide emulsion layer having a colloid/silver ratio based on the silver nitrate used in its production of not more than 1.5:1.

7. The process according to claim 5 in which the photographic emulsion colloid is gelatine.

8. The process according to claim 5 in which the colour formers employed each contain at least one aliphatic group containing at least five carbon atoms and at least one water-solubilizing group in the molecule.

9. A process for the production of a threecoloured subtractive photographic image which comprises coating a photographic base material with a first composition containing a silver halide and a colour former which is substantially nondiiiusing under the process conditions dispersed in a photographic emulsion colloid so as to produce, on drying, an emulsion layer containing a substantially normal coating weight of silver halide, printing from the first colour separating negative of a three colour set, coating the printed emulsion with a second composition containing silver halide and a second colour former of said non-diffusing type dispersed in the same emulsion colloid as that of said first applied composition so as to produce, on drying, a second emulsion layer, superposed upon the first printed emulsion and containing a substantially normal coating weight of silver halide, printing in register from the second colour separation negative of said three colour set, coating the second printed emulsion with a third composition containing silver halide and a third colour former of said non-diffusing type dispersed in the same 1 1 emulsion colloid as thatpf the first and second applied compositions so as to produce, on drying, a third emulsion layer superposed upon the second printed emulsion: and hayinga substantially normal coating weight of silverhalide, printing, in register, from the third colour separation negative of said threecolour set, the first, second and third colour formersbeing so chosen that upondevelopment-with a developer capable of formingdyes coloured images of correct hue are obtained, thereupon simultaneously developing the successively produced latentimageswith said developer and removing developed silver from saidi as .2 r I 10 A process according to claim 9 in whichall three emulsion layers have acolloid/silver ratio based on the silver nitrate used in their production of ,not-more than1-.5 to 1.

11. A process forrthe production of a threecoloured' subtractive photographic image which cQmprises coatingwa photographic base material witha first composition containing a silverhalide and a -colour former whichis substantially non diffusing under the process conditions dispersed in -a photographic emulsion colloid so as to produce, on dr ying, an emulsion layer containing a substantially normal coating weight of silver halide, printingfrom thefirst colour separating negative of a three colour set, coating the printed emulsion with a second composition containing 3 silver halide and? a thifdjlolo'urfforlfir ofsaid tiOIidiffusiilgty'p di'spersd'ifi"tlfe sain''effllllsiofi colloid as that orthe" first" al'id' second Y ap'pli'd compositions so-as toproduce; on: drying, a third emulsion-layer superposed-upon the second: printed emulsion--and-hav-ingasubstantially: normal coatingtweight of silver halide, printing, inregister, -irons thetthird colour separation negative'of said threecolourset, the first, second and third colour formersfb einge so chose'n that" upondevelopment with a developer capable of forming dyes coloured images of'correct hue'are obtained, simultaneously developing the successively pro duced latent images w'ith'a developer incapable of forming dyes from said colour formers, re moving unused silver halide, Zreconvertifig the developed silver images intosilver halide, reexposing and developing 'with a'deve'loper capable of" forming dyes from said :colo'ur' formers and removing developed sin/er from the images;

12. A process according to claim 11 in which all three emulsion layers have a colloid/silver ratio basedon the silverfnitrate used "in" their production of notmore thanfll5ito'. 11

JAC HOWARD c'ooTE."

REFERENCES CITED The following -references rare -:'0f record in the file of this patent: 

1. A PROCESS FOR THE PRODUCTION OF AS MULTICOLOURED PHOTOGRAPHIC IMAGE WHICH COMPRISES COATING A PHOTOGRAPHIC BASE MATERIAL WITH A FIRST COMPOSITION CONTAINING A SILVER HALIDE AND A COLOUR FORMER WHICH IS SUBSTANTIALLY NON-DIFFUSING UNDER THE PROCESS CONDITIONS DISPERSED IN A PHOTOGRAPHIC EMULSION COLLOID, PRINTING FROM A FIRST COLOUR SEPARATION RECORD, COATING THE PRINTED EMULSION WITH A SECOND COMPOSITION CONTAINING A SILVER HALIDE AND A COLOUR FORMER OF SAID NONDIFFUSING TYPE BUT ADAPTED TO PRODUCE A DIFFERENT COLOURED IMAGE, DISPERSED IN THE SAME PHOTOGRAPHIC EMULSION COLLOID AS THAT OF SAID FIRST COMPOSITION AS TO PRODUCE, ON DRYING, A SECOND SILVER HALIDE EMULSION LAYER DIRECTLY SUPERPOSED ON SAID PRINTED EMULSION, PRINTING IN REGISTER FROM A SECOND COLOUR SEPARATION RECORD, SIMULTANEOUSLY DEVELOPING THE SUCCESSIVELY PRODUCED LATENT IMAGES WITH A DEVELOPER CAPABLE OF FORMING DYES FROM SAID COLOUR FORMERS AND REMOVING DEVELOPED SILVER FROM THE IMAGES. 